The invention relates to a windscreen wiper device comprising an oscillating arm and a frame connected thereto for receiving a wiper blade, which frame includes a yoke which is pivotally connected to a carrier about a pivot axis, wherein both the carrier and the yoke are of at least substantially U-shaped cross section at the location of their interconnection, and wherein said yoke is positioned at least substantially within said carrier.
A windscreen wiper device of this kind is known from British patent No. 2,139,528 (Trico-Folberth Ltd.). In this prior art windscreen wiper device, each leg of the U-shaped cross section of the yoke includes a protrusion at the location of the pivot axis, which protrusion extends into a corresponding through hole in one of the legs of the U-shaped cross section of the carrier in the operating condition. In said operating condition, the yoke is pivots about a pivot axis relative to the yoke. Before the operating condition is reached, the yoke is first placed into the carrier, whereby the legs of the U-shaped cross section of the carrier occupy an initial position, that is, extend outwards relative to the yoke. Then the legs of the U-shaped cross section of the carrier are bent inwards by exerting an external force in inward direction relative to the yoke, wherein the protrusions of the yoke extend into the corresponding through holes in the carrier. The legs of the U-shaped cross section of the carrier remain in said bent position, thus securing the operating position.
One drawback of the windscreen wiper device as known from the aforesaid British patent publication is the fact that it has become apparent that it is not possible to cut or saw the above-indicated through holes in the legs of the U-shaped cross section of the carrier with sufficient precision. In practice this means that some play will develop between the protrusions of the yoke and the holes in the carrier after some time. This play will even increase as a consequence of the legs of the U-shaped cross-section of the carrier springing back in outward direction (relative to the yoke) after some time. In that case there is absolutely no question of a wear-resistant connection between the yoke and the carrier, nor of substantially frictionless pivoting of the yoke about the pivot axis. Consequently, there is absolutely no question of a durable connection between the yoke and the carrier in accordance with the aforesaid British patent. Another drawback of the prior art windscreen wiper device is the fact that in particular dirt can accumulate in the through holes that are present in the legs of the U-shaped cross section of the carrier, which likewise affects the durability of the connection between the yoke and the carrier.
The object of the invention is to overcome the above drawbacks of the prior art and in particular to provide a windscreen wiper device wherein the connection between the yoke and the carrier is durable and solid, i.e. wherein particularly there is no angular play between the carrier and the yoke.
In order to accomplish that objective, a windscreen wiper device of the kind mentioned in the introduction is according to the invention characterized in that the carrier includes a closed substantially cylindrical protuberance in each leg of the U-shaped cross section at the location of the pivot axis, which protuberance forms a substantially cylindrical bearing surface. In one preferred variant, the protuberances extend outwards on either side relative to the yoke, the yoke being provided at the location of the pivot axis with a protrusion in each leg of its U-shaped cross section, which protrusion pivotally engages in a corresponding protuberance of the carrier. Since the protuberances extend outwards, the two protrusions of the yoke, which function as bearing supports, are spaced relatively far apart, as a result of which the forces on said bearings are relatively small. In another preferred variant, the protuberances extend inwards on either side relative to the yoke, wherein the yoke includes a recess in each leg of its U-shaped cross section, at the location of the pivot axis, in which a corresponding protuberance of the carrier pivotally engages. In this connection, the term xe2x80x9cclosed protuberancexe2x80x9d is understood to mean a dished part, that is, a part of the material of the legs of the U-shaped cross section of the carrier that is locally pushed aside, in such a manner that no opening in the sense of a through hole is formed. In the former preferred embodiment, the material is pushed outwards, whilst in the latter preferred embodiment the material is pushed inwards. An important advantage of the closed protuberance or dished part is that the shape thereof can be determined with great precision by stamping or punching, so that there is no question of play between the yoke and the carrier. Another advantage is furthermore the fact that dirt from outside cannot accumulate in the protuberances.
In one preferred embodiment of a windscreen wiper device according to the invention, the yoke is externally formed with a longitudinal groove in at least one leg of its U-shaped cross section, along which groove a protuberance of the carrier is guided when the yoke is at least substantially received in the carrier in the longitudinal direction of the carrier. This enables sliding movement of the yoke in the carrier in the longitudinal direction of said carrier, wherein the former longitudinal groove functions as a guide for a protuberance of the carrier, in which case said protuberance extends inwards relative to the yoke, of course.
The invention furthermore relates to a method of S manufacturing a windscreen wiper device according to the invention, wherein the two closed protuberances are stamped in the sheet material from which the carrier is made before the material is given its U-shaped section. In one preferred embodiment, the yoke is placed at least substantially within the carrier and connected thereto in an initial position, in which protrusions formed in the legs of the U-shaped cross section of the yoke engage at least partially at the location of the pivot axis in protuberances of the carrier extending outwards on either side relative to the yoke, thus leaving some play between the yoke and the carrier, and wherein the yoke is then connected to the carrier in a final position, without play, by bending the legs of the U-shaped cross section of the carrier inwardly relative to the yoke. In another preferred embodiment, the yoke is placed at least substantially within the carrier and connected thereto in an initial position, wherein protuberances of the carrier extending inwards on either side relative to the yoke engage at least partially at the location of the pivot axis in recesses formed in the legs of the U-shaped cross section of the yoke, thus leaving some play between the yoke and the carrier, and wherein the yoke is then connected to the carrier in a final position, without play, by bending the legs of the U-shaped cross section of the carrier inwardly relative to the yoke. In both embodiments the protuberances according to the invention are dimensioned such that, even when the legs of the U-shaped cross-section of the carrier will spring back a little bit in outward direction relative to the yoke after being bent in inward direction in the final position, angular play between the carrier and the yoke does not occur.
It is noted that from French patent No. 2,453,757 (Ducellier et Cie.) a connecting construction is known wherein a convex protrusion is present on each leg of the U-shaped cross section of the yoke, which protrusion fits in a corresponding recess in each leg of the U-shaped cross section of the carrier. A cylindrical bearing surface is not provided here, however, so that there is absolutely no question of a properly functioning and reliable connection between the yoke and the carrier.